This invention generally relates to expansion of tubular members and more particularly relates to an eddy current probe apparatus having an expansible sleeve thereon capable of hydraulically diametrically expanding a tube into engagement with a tube sheet or tube support plate and capable of hydraulically diametrically expanding a tubular sealing member into engagement with the interior wall of the tube, which probe is also capable of detecting the location of the tube sheet or support plate and the extent of diametrical expansion of the sealing member and tube.
It is well known that in a nuclear reactor power plant a steam generator generates steam when heat is transferred by conduction from a radioactive primary fluid to a non-radioactive secondary fluid through a heat conductor boundary separating the primary fluid from the secondary fluid. As the temperature of the secondary fluid increases, the secondary fluid reaches saturation temperature beyond which saturation temperature increasing fractions of the secondary fluid enter the vapor phase thereby producing steam. The steam generator typically includes a plurality of tubes through which the primary fluid flows. The walls of these tubes function as the heat conductor boundary for conducting heat from the primary fluid to the secondary fluid. Typically, each tube is supported along its length by a plurality of tube support plates having holes therein for receiving each tube. Moreover, the ends of each tube are typically supported by a tube sheet having apertures therein for receiving each tube. The terminal ends of each tube are typically attached to the tube sheet by welding. As discussed below, although the support plates and tube sheet provide support for each tube, a gap may exist in the hole at the interface of the tube and support plate or in the aperture at the interface of the tube and tube sheet. Thus, a gap may exist between the tube and the support plate or between the tube and the tube sheet.
As indicated above, the primary fluid flowing in the steam generator tubes is radioactive; hence, the steam generator is designed such that the radioactive primary fluid does not radioactively contaminate the secondary fluid by mingling with the secondary fluid. It is therefore desirable that the tubes remain leak-tight so that radioactive primary fluid remains everywhere separated from the secondary fluid to avoid mingling the radioactive primary fluid with the secondary fluid.
Occasionally, due to vibration and tube wall intergranular cracking caused by stress and corrosion during operation, the steam generator tubes may develop surface and volume flaws and thus may not remain leak-tight. If through-wall cracking occurs due to the flaws, the radioactive primary fluid may mingle with the secondary fluid. The through-wall cracking may occur in a tube portion adjacent the gap due to tube vibration and intergranular stress corrosion cracking at that location. As explained presently, these gaps between the tube and the support plate or between the tube and the tube sheet may lead to deterioration of the tube at the location adjacent the gap due to flow induced vibration of the tube against the support plate or tube sheet thus wearing the tube and due to deposition of contaminates within the gap thus constricting, stressing and corroding the tube. Hence, precautionary measures may be necessary to ensure that surface and volume flaws caused by vibration, stress and corrosion do not develop in the tubes so that mingling of the radioactive primary fluid with the secondary fluid is avoided. It would be desirable to provide an apparatus to expand the tube having flaws therein into engagement with the tube sheet or with the support plate so that the gap is closed or to sleeve the tube having the flaws.
However, before the tube may be expanded to close the gap, the location of the support plate or tube sheet should first be precisely determined so that the tube may be precisely diametrically expanded against the support plate or tube sheet. Moreover, it is desirable that the extent of diametrical expansion of the tube be precisely continuously monitored so that the tube suitably closes the gap or so that the tube is suitably sleeved in a predetermined manner. However, one problem in the art has been to provide an eddy current device for precisely determining the location of the support plate or tube sheet and for determining the diametrical expansion of the tube. Moreover, because it may be desirable to use hydraulic means to expand the tube, yet another problem in the art has been to provide an eddy current device capable of resisting the relatively high pressures experienced by the eddy current device in the instance when the tube is hydraulically expanded.
There are several eddy current probe devices known in the art for expanding tubular members. One such device is disclosed by U.S. Pat. No. 4,159,564 issued July 3, 1979 in the name of Frank W. Cooper, Jr. entitled "Mandrel for Hydraulically Expanding a Tube into Engagement with a Tubesheet" and assigned to the Westinghouse Electric Corporation. The Cooper, Jr. patent is directed towards hydraulically expanding tubes in a tube sheet of a heat exchanger and comprises a mandrel with an eddy current coil for detecting the inner edge of a tube sheet. The mandrel further includes a body portion having a leading and trailing end. The body portion has an elongated groove in each end thereof and an elastomer sealing member disposed in each groove. The mandrel also includes passages disposed in the trailing end for introducing pressurized fluid between the grooves, whereby the pressurized fluid is contained between the sealing members, the mandrel, and the tube to hydraulically expand the tube into engagement with the tube sheet without using an expansible sleeve. The eddy current coil is connected to the mandrel at the leading end on the out-board side of the grooves. However, the Cooper, Jr. patent does not appear to disclose an eddy current probe apparatus having an expansible sleeve for expanding a tube into engagement with a tube sheet or tube support plate.
Another eddy current probe device capable of expansibly engaging a tube for inspecting the tube for flaws is disclosed by U.S. Pat. No. 4,303,884 issued Dec. 1, 1981 in the name of Franklin S. Malick entitled "Inflatable Eddy Current Inspection Probe for Inspection of Tubular Means" and assigned to the Westinghouse Electric Corporation. This patent discloses a device comprising a plurality of axially oriented plastic strips which form the circumference of the probe with each plastic strip having mounted thereon an eddy current coil. A rubber tube is disposed on the interior of the plastic strips so that when the rubber tube is inflated, the plastic strips and coils are forced outward into close contact with the tube so that the eddy current coils can detect flaws in the tube. Although the Malick patent may disclose an inflatable eddy current inspection probe, the Malick patent does not appear to disclose an eddy current probe having a cylindrical sleeve capable of expanding a tube into engagement with a tube sheet or support plate in the manner of the present invention.
A device for expanding tubular members is disclosed by U.S. Pat. No. 4,195,390 issued Apr. 1, 1980 in the name of Randall M. Amen and entitled "Apparatus and Method for Manipulation and Sleeving of Tubular Members". The Amen device includes a hollow, elastic, tubular bladder held on an elongate connection member or tie rod sealably positioned therewithin by means of a pair of end caps with means for providing fluid communication to the sealed interior of the bladder. With the expansion apparatus positioned within a tubular member and hydraulic fluid pumped into the bladder, the bladder will expand the tubular member beyond its elastic limit. Although the Amen patent may disclose a device having a tubular bladder that can expand a tubular member, the Amen patent does not appear to disclose an eddy current probe apparatus capable of detecting the location of a tube sheet or support plate and capable of detecting the extent of diametrical expansion of the tubular member.
Yet another device for expanding tubular members is disclosed by U.S. Pat. No. 4,513,506 issued Apr. 30, 1985 in the name of John P. Vogeleer entitled "Measuring of Tue Expansion" and assigned to the Westinghouse Electric Corporation. The Vogeleer patent is directed towards measurement of the expansion of the tubes or sleeves in tubes of a steam generator of a nuclear reactor plant. The expansion is produced by pressure of a fluid which is transmitted to the part of the tube or sleeve which is being expanded. An expansion mandrel or expander body is inserted into the tube or sleeve. A pressure fluid flows through a fluid conductor, into a channel in the mandrel and thence in contact with the tube or sleeve to be expanded. An elongated member extends through the channel and through the conductor to a position outside of the conductor. A plurality of transverse or radial captive pins or plungers extend through the mandrel between the elongated member and the tube or sleeve. Radial movement of the captive pins as the tube or sleeve is expanded produces movement of the elongated member. A dial, connected to the elongated member continuously measures the magnitude of the movement of the elongated member as the tube or sleeve is expanded. According to this patent, the expansion of the tube or sleeve as it expands is thus known and may be controlled. Although this patent discloses a device for measuring tube expansion, this patent does not appear to disclose an eddy current probe apparatus having an expansible sleeve thereon capable of diametrically expanding a tube, which probe is capable also of detecting by use of eddy currents the location of a tube sheet or support plate and the extent of diametrical expansion of the tube as provided by the present invention.
Consequently, while the prior art discloses devices for expanding tubular members, the prior art does not appear to disclose an eddy current probe apparatus for expanding a tube into engagement with a tube sheet or tube support plate, which device is capable of detecting the location of the tube sheet or support plate and also capable of detecting the extent of diametrical expansion of the tube in the manner of the present invention.
Therefore, what is needed is an eddy current probe apparatus having an expansible sleeve thereon capable of hydraulically diametrically expanding a tube into engagement with a tube sheet or tube support plate and capable of hydraulically diametrically expanding a tubular sealing member into engagement with the interior wall of the tube, which probe is also capable of detecting the location of the tube sheet or support plate and the extent of diametrical expansion of the sealing member and tube.